Relationships between skull size and body mass in primates

The primary goal of this project was to establish a skull size dataset for all primates and begin comparing aspects of these data with overall body size (mass). In order to estimate skull size, 28 skull dimensions were measured to the nearest 0.01mm and cranial and mandibular mass were weighed to the nearest 0.1g. These measurements attempt to capture all the major regions of the skull and were evaluated both individually and collectively by calculating a geometric mean of skull size. In total, over 3500 dry specimens were investigated representing every accessible species of primate (~ 250) from the collections at several major museums in the United States (AMNH, FMNH, USNM, MCZ). Body mass estimates were taken from the literature although body mass data were also collected for individual museum specimens whenever these data were available.

Overall, there is a highly significant negative allometric relationship between body mass and the geometric mean of skull size. However, individual taxonomic groups demonstrate significant differences in relative skull size (skull size / body mass). For example, platyrrhines have relatively larger skulls than catarrhines, and tarsiers have the relatively largest skulls of any primate. Considering sexual dimorphism, patterns between body mass and skull size are highly correlated, although the degree of dimorphism is generally lower when evaluated using skull size compared to body mass. Individual cranial measurements were also evaluated for their ability to predict body mass, and the results were highly dependent on the taxonomic level used for the analysis (order, superfamily, etc.).

Funding to M.N.C. for museum travel was provided by Midwesten University.